From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-179.mta1.migadu.com (out-179.mta1.migadu.com [95.215.58.179]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F05A816CD12 for ; Mon, 5 Aug 2024 23:27:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.179 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722900427; cv=none; b=nDn4EirUm+T+RBr3XBi4INI66LQzYSEkWYYW8jNwCJQTCd9gFNE/u9+YvyNyYtCeqh+zqamu96MjyJe12RSnKOngsEEBXMoFWEoXj1z6YIuAYFckX/4iprmeH0KeFCdlOuI+WDaUqcGahTpAxWFY+OLlG4fLul42kO+bSqJNHi0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722900427; c=relaxed/simple; bh=TGXOf7/1guqVacY7V5I/og3eT0WLPefs7Me46InMVQI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=dpHf6u/QiHzxzZG0xPIT5Q+Rc1TkTtUnCG8QCiWHURXlaN8NC78mMmg89mKEDU1imgjCLPjydXbaHAyzU2uzaalhmPJjX3tBR9Mpyi4F5KMr9vm/ejlkBOVUfvuHvFji8cNtTHVwysBMoV93OHKFeyNq9SaPwMG3d5VL+55vjhM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=RKwoJraZ; arc=none smtp.client-ip=95.215.58.179 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="RKwoJraZ" Date: Mon, 5 Aug 2024 23:26:54 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1722900421; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=N/Y4ENu+y9slWM0GBwHxlJjHc94wXfdkp05Gs7ZabqI=; b=RKwoJraZF8EcCuf9Yeaydj7V+54xjIFKFDGqqwUhB7a+wtctICJfGkJrTsxTgXHoUCGmr/ MxT6+GXFZukzNHF22AQeMcjuXCNYLrDgYRshsfdGgn8o53cA/EySOVyTW+EnxUHWDvXDVo mtK4xMi/hhtI0dNWL878kUCnrmNBHXM= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Sean Christopherson Cc: Paolo Bonzini , Marc Zyngier , Tianrui Zhao , Bibo Mao , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, David Matlack , David Stevens , Fuad Tabba Subject: Re: [PATCH v12 54/84] KVM: arm64: Mark "struct page" pfns accessed/dirty before dropping mmu_lock Message-ID: References: <20240726235234.228822-1-seanjc@google.com> <20240726235234.228822-55-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT On Mon, Aug 05, 2024 at 11:26:03PM +0000, Oliver Upton wrote: > [+cc Fuad] Take 2! > Fuad, you mentioned in commit 9c30fc615daa ("KVM: arm64: Move setting > the page as dirty out of the critical section") that restructuring > around the MMU lock was helpful for reuse (presumably for pKVM), but I > lack the context there. > > On Fri, Jul 26, 2024 at 04:52:03PM -0700, Sean Christopherson wrote: > > Mark pages/folios accessed+dirty prior to dropping mmu_lock, as marking a > > page/folio dirty after it has been written back can make some filesystems > > unhappy (backing KVM guests will such filesystem files is uncommon, and > > typo: s/will/with/ > > > the race is minuscule, hence the lack of complaints). See the link below > > for details. > > > > This will also allow converting arm64 to kvm_release_faultin_page(), which > > requires that mmu_lock be held (for the aforementioned reason). > > > > Link: https://lore.kernel.org/all/cover.1683044162.git.lstoakes@gmail.com > > Signed-off-by: Sean Christopherson > > --- > > arch/arm64/kvm/mmu.c | 10 ++++++---- > > 1 file changed, 6 insertions(+), 4 deletions(-) > > > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > > index 22ee37360c4e..ce13c3d884d5 100644 > > --- a/arch/arm64/kvm/mmu.c > > +++ b/arch/arm64/kvm/mmu.c > > @@ -1685,15 +1685,17 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > > } > > > > out_unlock: > > + if (writable && !ret) > > + kvm_set_pfn_dirty(pfn); > > I'm guessing you meant kvm_release_pfn_dirty() here, because this leaks > a reference. > > > + else > > + kvm_release_pfn_clean(pfn); > > + > > read_unlock(&kvm->mmu_lock); > > > > /* Mark the page dirty only if the fault is handled successfully */ > > - if (writable && !ret) { > > - kvm_set_pfn_dirty(pfn); > > + if (writable && !ret) > > mark_page_dirty_in_slot(kvm, memslot, gfn); > > - } > > > > - kvm_release_pfn_clean(pfn); > > return ret != -EAGAIN ? ret : 0; > > } > > > > -- > > 2.46.0.rc1.232.g9752f9e123-goog > > > > -- > Thanks, > Oliver -- Thanks, Oliver